Other chapters consider young-onset and rapidly progressive dementia. Here we consider dementia in people 65 years of age and older.
SCIENCE REVISITEDEpidemiology
In 2010, dementia was estimated to affect 35.7 million people world-wide. Alzheimer’s disease is the most common dementia in people older than age 65 years, yet Alzheimer’s disease pathology is often accompanied by vascular disease or Lewy bodies. The latter two types of dementia can also occur in “pure” form. The diagnosis of dementia increases mortality risk, regardless of age or etiology of dementia. It is important to recognize that dementia may lead to a debilitated state and death in order to direct interventions appropriately, including palliative approaches. Prediction of death can be challenging in patients with dementia, which may make initiation of formal palliative care services difficult. (Chapter 9 provides a detailed discussion of the role of palliative care in dementia.)
Assessment
History
Obtaining an accurate medical history is central to the diagnosis of dementia. This should identify and qualify the nature of the symptoms as well as their onset and progression. A critical challenge to obtaining an accurate history is that patients themselves may not be able to self-monitor because of their cognitive problems, so obtaining a collateral history is necessary. Memory impairment is a central feature of many dementias and can be expected to interfere with recall of key historical events. In addition, lack of insight can occur in dementia and interfere with the acknowledgment of symptoms. It is important to interview the informant and patient separately at some point in the diagnostic process. While some standardized questionnaires are useful in identifying complaints, these do not replace a thorough history, which remains the gold standard. Instruments that can complement the clinical history include the AD8 dementia screening questionnaire, the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE), the Deterioration Cognitive Observation Scale (DECO), and the Alzheimer Questionnaire (AQ). The General Practitioner Assessment of Cognition (GPCog) includes both a cognitive screen and questions regarding cognitive changes and activities of daily living based on caregiver report, which improves sensitivity and specificity for the diagnosis of dementia.
While the initial focus of the history should be on cognitive complaints and their functional implications, which allow for meeting dementia criteria, psychiatric and behavioral changes need to be identified as they are often present in early dementia, and can be prominent in some patients. In many patients referred for cognitive decline, psychiatric issues may predominate and may be the cause of the so-called cognitive decline. Depression should routinely be assessed in patients with cognitive complaints. It is key to screen for depressive symptoms, and scales such as the Geriatric Depression Scale, which has 15- and 30-item versions (www.stanford.edu/~yesavage/GDS.html), and the Montgomery-Asberg Depression Scale, can be helpful in this regard, though the gold standard is a psychiatric evaluation using a standardized interview schedule. The Cornell Scale for Depression in Dementia is validated for the dementia population. Depression can be a risk factor for or coincident with the diagnosis of dementia. Moreover, it can occur de novo in the course of dementia. Although they are distinct symptoms, depression and anxiety often co-exist. Other mood symptoms, such as elation or euphoria, also can occur in dementia, but primary psychiatric disorders should be kept in the differential diagnosis if these are prominent.
While not absolute, the nature of cognitive deficits can help in differentiating depression from dementia. Patients with depression have long response latencies whereas typical patients with Alzheimer’s disease respond with normal latencies. Memory impairment in depression is related to retrieval problems, rather than problems with encoding, where cueing does not improve recall. Alzheimer’s patients also have additional cognitive deficits, particularly in visuospatial and language domains, that would not be seen in depression. As noted, depression can co-exist with dementia and it is common in Alzheimer’s disease as well as vascular dementia and dementia with Lewy bodies.
Other neuropsychiatric problems that should be considered include positive symptoms such as disinhibition, irritability, agitation, aggression, or abnormal motor behavior as well as negative symptoms such as apathy. Delusions and hallucinations are also highly relevant. These symptoms can be assessed using standardized instruments such as the Neuropsychiatric Inventory (NPI). They can occur early in the course of dementia and can evolve over time. The Frontal Behavior Inventory can help with the differentiation of Alzheimer’s disease from frontotemporal dementia. Patients with frontotemporal dementia often lack emotional responsiveness and can develop apathy, which can be mistaken for depression but is characterized by lack of motivation. Psychotic features, particularly visual hallucinations, are characteristic of PDD and DLB. Delusions are not as specific but can be equally disturbing to family members.
It is critical to identify functional impairment. By definition, patients with mild cognitive impairment (MCI) do not have substantial functional impairment, while patients with dementia do. Practically speaking, at the time of diagnostic evaluation, assessment of basic and instrumental activities of daily living is performed by asking the patient and their caregiver how the patient performs everyday tasks. Basic activities of daily living such as getting in and out of bed, dressing, walking, toileting, bathing, and eating are not affected early in the course of dementia. Instrumental activities of daily living (IADL) such as answering the phone, taking pills, handling money, shopping, cooking, and driving are affected early in the course.
Typically a standardized questionnaire is used to address activities of daily living. Examples include the Functional Activities Questionnaire (FAQ) which addresses IADLs, the Lawton and Brody IADL and Physical Self-Maintenance Scale and the OARS Functional Assessment Questionnaire. Assessment is not as straightforward as it seems, as there is often a mild degree of functional impairment in MCI, where such impairments may predict future cognitive decline. Moreover, a given patient’s living situation might not tax their functional capacity. Conversely, a patient who is working might have some workplace impairment despite relatively well-preserved cognitive assessment. In the setting of a disorder that affects motor function, such as Parkinson’s disease or after a stroke, it can be challenging to determine if a change in a patient’s function is related to cognitive or motor function.
Prescribed and over-the-counter medications, as well as substances of abuse (notably alcohol), are important to identify as they might contribute to cognitive impairment. If the patient is not able to list these accurately, this suggests an important area of functional impairment that requires intervention. All co-morbid medical conditions need to be identified. Vascular risk factors such as smoking, diabetes, obesity, hyperlipidemia, hypertension, atrial fibrillation, and non-central nervous system (CNS) vascular disease (cardiac, renal, peripheral) increase the risk for cerebrovascular events, which can contribute to dementia, and can be covert. These are risk factors for dementia in the absence of identifiable stroke as well. Symptoms suggestive of cancer, especially in patients with a rapid course, raise the concern of direct or indirect central nervous system involvement.
A detailed family history is critical. While familial dementia commonly has a young onset, risk of dementia in older people is also increased in the setting of a family history. A third to half of people with frontotemporal dementia have a family history compared to roughly one in 10 patients with Alzheimer’s disease. At a minimum, all first-degree relatives should be identified and the presence of neurological disorders determined. This history should not be restricted to examining dementia risk, since disorders such as Parkinson’s disease and motor neuron disease may be associated with an increased risk of dementia in family members. If the family history is consistent with a hereditary dementia, testing can be offered but this should be done after appropriated counseling. At-risk family members should only be tested after genetic counseling. Huntington’s disease is a relatively common cause of dementia in younger individuals, but can occasionally be identified for the first time in older patients without an obvious family history.
Physical examination
General examination
The general examination might identify specific co-morbid conditions, such as atrial fibrillation, congestive heart failure or chronic obstructive pulmonary disease (COPD). An abdominal or rectal mass, suggesting a neoplasm, might be uncovered. These might directly or indirectly contribute to cognitive dysfunction. Some findings on general examinations, such as postural hypotension, may suggest a specific diagnosis such as dementia with Lewy bodies.
Cognitive evaluation
Cognitive assessment at the bedside is important for both differential diagnosis and rating the severity of cognitive impairment. Cognitive domains to be assessed correspond to those involved in the diagnosis, including attention, orientation, memory, executive function, language, praxis, and visuospatial abilities.
Several standardized assessment instruments have improved clinicians’ abilities to assess cognition. While these are helpful, the clinician needs to be able go beyond such instruments at times, given their limitations in scope and sensitivity. The Mini-Mental Status Examination (MMSE) is the most commonly used instrument and its advantages include its widespread use and extensive validation. Disadvantages include its relative insensitivity to the diagnosis of dementia, which may be partly related to exclusion of some cognitive domains, such as executive function. Given the availability of superior instruments, its use will likely decrease over time. The MMSE may not be sensitive to memory impairment since it only relies on the immediate recall of three words. Expanded versions of the MMSE such as the 3MS might have increased sensitivity. More comprehensive standardized instruments include the Short Portable Mental Status Examination, the Montreal Cognitive Assessment (MOCA) (www.mocatest.org), and the Addenbrooke Cognitive Examination-Revised. The Frontal Assessment Battery evaluates aspects of frontal lobe function, and can be used as a complement to tools such as the MMSE that do not specifically address this cognitive domain. It can assist in the differentiation of AD from frontotemporal dementia and may be useful in assessing parkinsonian disorders.
Neuropsychological testing, which affords a comprehensive, objective, and standardized approach to quantifying cognitive impairment, is helpful for diagnosis and differential diagnosis, but is not available in all settings. It is particularly relevant in mild or questionable cases, in cases where malingering is suspected, or in subjects for whom ceiling or floor effects might obscure interpretation of results on simplified tests (for example, people with very high or very low levels of education). Patients with clear changes and obvious deficits on simpler tests may not require neuropsychological testing. Moreover, it should be borne in mind that subjects may have test scores that are abnormal based on statistical population-based comparison but that this may represent a “normal” score or minimal change for that individual. Neuropsychological tests can be helpful in following change over time. The shorter tests do not necessarily validly assess cognitive subdomains as can be done by neuropsychological batteries, which may be important in differential diagnosis.
TIPS AND TRICKS- In patients with worrisome history but good performance on mental status exam.
- In cases where malingering is suspected.
- To distinguish depression with cognitive symptoms from neurodegenerative disease.
Neurological examination
A complete general neurological examination is important. On cranial nerve testing, olfactory deficits are common in Lewy body dementia. Visual field defects or higher order visual defects may suggest cerebrovascular disease affecting the visual pathways or a posterior evolving dementia, such as the visual variant of AD or the Heidenhain variant of Creutzfeldt–Jakob disease (CJD). Other cranial nerve examination clues to the etiology of dementia can include vertical supranuclear gaze difficulty suggesting progressive supranuclear palsy. Nystagmus and restricted eye movement can be seen in Wernicke’s encephalopathy, which can evolve into alcoholic dementia. Gaze-evoked nystagmus is non-specific and be seen with many causes of cerebellar degeneration. Upper motor neuron facial weakness suggests pyramidal involvement. Lower motor neuron facial weakness and involvement of other lower cranial nerves may provide a clue to involvement of the subarachnoid space due to an inflammatory, neoplastic or infectious process. Bulbar difficulties are seen in processes involving the brainstem or upper motor neuron lesions.
Focal weakness with other pyramidal signs can be seen in patients with cerebrovascular disease. Pyramidal signs can also be a clue to the presence of motor neuron disease (amyotrophic lateral sclerosis – ALS), in which features of lower motor neuron dysfunction can also be found (fasciculations, atrophy). Up to 10% of frontotemporal dementia patients can develop features of ALS, which has a substantial impact on prognosis and hence on long-term planning.
Cerebellar dysfunction in dementia might indicate a specific neurodegenerative disorder such as multiple system atrophy, a paraneoplastic disorder, CJD or celiac disease.
Neuropathy can be seen in renal failure, diabetes, vitamin B12 deficiency, alcohol exposure or paraneoplastic disorders. Neuropathy can also be seen in HIV, Lyme disease or hepatitis C infections which all can be associated with cognitive impairment and dementia. In addition, some mitochondrial disorders or disorders of central white matter (leukodystrophies) can be associated with neuropathy. Mitochondrial disorders are also classically associated with myopathy, myoclonus, and seizures.
Gait assessment is critical in patients with dementia. While it is less often impaired in AD, it is commonly affected in PDD, vascular dementia, and dementia with Lewy bodies.
It is important to examine for adventitious movements. The triad of tremor (rest tremor), bradykinesia, and rigidity indicates parkinsonism, as seen in dementia with Lewy bodies or Parkinson’s disease. Chorea would suggest Huntington’s disease, neuroacanthocytosis or another Huntington-like disorder. Dystonia in older adults may suggest a cerebrovascular event, either in the basal ganglia or thalamus. In addition to dystonia, unilateral chorea or tremor in an older adult should lead to consideration of a cerebrovascular event or other lesion, generally involving frontostriatal circuits, which can additionally be involved in cognition.
Myoclonus can be seen in degenerative disorders, including advanced AD and DLB, and more rarely Huntington’s disease and frontotemporal dementia. Focal myoclonus as well as asymmetrical apraxia, parkinsonism, and dystonia is characteristic of corticobasal ganglionic degeneration. Myoclonus is included in the diagnostic criteria of CJD, though it may not be seen early in the illness. When CJD is considered, it is important to keep alternative entities in mind. In terms of systemic illness, myoclonus is most often a manifestation of any cause of encephalopathy, including common disorders such as renal or hepatic disease (asterixis), as well as rarer autoimmune disorders such as steroid-responsive encephalopathies associated with thyroid disease or antibodies to the CNS. Rare disorders such as mitochondrial disease are characterized by myoclonus.
Laboratory studies
Blood and spinal fluid
Recommended tests for the assessment of dementia include blood work-up, including complete blood count (CBC), glucose, electrolytes (including calcium), renal and hepatic tests and thyroid function. Testing for vitamin B12 or folate deficiency is recommended. In many areas grains are supplemented with folate, making folate deficiency unlikely unless there are other reasons for malabsorption, in which case malabsorption of other B-vitamins should be considered. If indicated, based on the patient’s history, assessment for chronic infections that can cause dementia, such as HIV or syphilis, is indicated.
If the presentation suggests a delirium additional testing should be done to rule out possible causes of delirium such as acute infections (cultures, chest x-ray, urinalysis). Work-up for inflammatory or autoimmune disorders should also be considered. The erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) or more specific tests such as rheumatoid factors and antinuclear antibodies can provide clues to the presence of an autoimmune disorder. Additional work-up is indicated if specific disorders such as vasculitis, Sjögren’s syndrome, sarcoidosis or a paraneoplastic or non-paraneoplastic autoimmune encephalopathies are being considered.
A complete work-up may include cerebrospinal fluid (CSF) examination, which can also be used to seek evidence for acute or subacute infections, autoimmune or inflammatory disorders or neoplastic involvement of the central nervous system. While proteins in the CSF, such as beta-amyloid, tau and phosphorylated tau, can be used to provide evidence for AD, these tests are not currently used routinely. This may change as additional evidence accumulates for their utility in treatment decisions, and they become more readily available. The use of CSF markers in the differential diagnosis of CJD is controversial, because the markers (14-3-3, tau, S100B) are non-specific. Nevertheless, CSF examination is important in rapidly progressive dementia to rule out or rule in treatable dementia and the CSF markers may improve diagnostic certainty in the appropriate clinical context.
Imaging
Structural imaging (computed tomography [CT] or magnetic resonance imaging [MRI]) scans can rule out structural contributions to cognitive decline (stroke, subdural hematoma, tumors) and are increasingly being used to “rule in” specific diagnoses, when atrophic or vascular changes are observed that are consistent with a particular dementia diagnosis. While MRI is more sensitive than CT, CT scans can still provide meaningful information. For example, vascular changes, subdural hematomas and many tumors, while better delineated on MRI, can be seen quite well on modern CT scans. Similarly hydrocephalus can be identified on CT in cases of suspected normal pressure hydrocephalus (NPH). In NPH and other forms of hydrocephalus, MRI allows examination of the posterior fossa to search for lesions that might lead to obstruction of CSF flow. An absence of ventricular enlargement on CT can exclude NPH and help to redirect further investigation and diagnostic considerations. A caution in interpreting ventricular enlargement is that it might be due to global atrophy.
In addition to better resolution, specific MRI approaches (such as gradient echo MRI) can identify findings such as cerebral microbleeds, which are not evident on CT. These suggest amyloid angiopathy and are often seen in association with white matter disease, which is found patients with vascular cognitive impairment or dementia. MRI imaging might help to discern an atrophy pattern consistent with degenerative syndromes such as progressive supranuclear palsy PSP, multiple system atrophy (MSA) or corticobasal ganglionic degeneration. Brain atrophy is less prominent in DLB and PDD than in AD and it is not prominent in PD until cognitive decline ensues. On the other hand, atrophy is prominent in frontotemporal lobar degenerations.
Dopamine transporter imaging (123I-fluoropropyl-2-beta-carbomethoxy-3-beta(4-iodophenyl)nortropane single photon emission computed tomography: FP-CIT SPECT) is useful in differentiating DLB from dementias that do not affect the dopaminergic system. Functional studies examining perfusion (Tc-hexamethylpropyleneamine oxime [HMPAO] SPECT) or glucose metabolism (fluorodeoxyglucose [FDG] positron emission tomography [PET]) provide additional information that can be useful in the differential diagnosis of dementia. Building on previous work with the C-11 compound Pittsburgh Compound B (PIB), the availability of readily accessible ligands, such as F-18-fluorbetapir, that can bind amyloid will likely assist in differential diagnosis but, as with all imaging modalities, will have to be interpreted in the clinical context. Newer techniques are becoming available that examine brain networks and their connectivity.
Types of dementia
Specific features of the history, examination, and investigations can assist in the differential diagnosis of dementia (Figure 1.1, Table 1.2). After reversible conditions have been ruled out, the clinician should attempt to make a specific diagnosis of dementia type. The most common causes of dementia are Alzheimer’s disease, vascular dementia, Lewy body dementia, and frontotemporal dementia. Here some features of particular importance are discussed.
Related posts:
An Approach to the Problem of Normal Pressure Hydrocephalus
Palliative Care in Advanced Dementias
Depression: Cause or Complication of Cognitive Decline?
After the Diagnosis: Continuing Neurological Care of the Outpatient with Dementia
Using Psychotropic Medications to Manage Problem Behaviors in Dementia
Young Onset Dementia: How Much Diagnostic Testing is Enough?
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